1 - Upload the file clicking below were says "click here", but be careful: when uploading name the file attached like this: YourNameofFirstAuthor_et_al.pdf

2 - After uploading, edit this WIKI (see edit button on the top right corner), add one empty line and the following line at the bottom of the next section "Abstracts already uploaded":
'''Abstract by YourNameofFirstAuthor et al''': [[Attach:YourNameofFirstAuthor_et_al.pdf | Abstract by YourNameofFirstAuthor et al]]